PB – frames and Improved PB – frames Mode
The PB frame consists of a P picture and a B picture in the same frame. The blocks for the P frame and the B frame are interleaved so that a macroblock consists of six blocks of a P picture followed by six blocks of a B picture. The motion vector for the B picture is derived from the motion vector for the P picture by taking into account the time difference between the P picture and the B picture. If the motion cannot be properly derived, a delta correction is included. The improved PB-frame mode updates the PB-frame mode to include forward, backward, and bidirectional prediction
Advanced Intra Coding Mode in data compression
The coefficients for the I frames are obtained directly by transforming the pixels of the picture. As a result, there can be significant correlation between some of the coefficients of neighboring blocks. For example, the DC coefficient represents the average value of a block. It is very likely that the average value will not change significantly between blocks. The same may be true, albeit to a lesser degree, for the low-frequency horizontal and vertical coefficients. The advanced intra coding mode allows the use of this correlation by using coefficients from neighboring blocks for predicting the coefficients of the block being encoded. The prediction errors are then quantized and coded.